The USSR never claimed to have “achieved communism”. I know there are Marxists who claim that the USSR wasn’t even properly socialist, but this sort of doctrinal bickering doesn’t make any historical difference until it reaches somewhere outside the realm of fringe radical movements and academic ivory towers. And even then, the power dynamics of the differing groups of adherents matter a lot more than the doctrinal nitpicking, just as with any other sectarian dispute.
Arguing about whether the Soviets were “true” Marxists is like arguing about whether the Roman Catholic Church is the “true” “catholic and apostolic church” of the Nicene Creed; at some point everyone who isn’t a theologian taking a break from the equally important “angels dancing on the head of a pin” problem just uses the word “Catholic” to refer to the biggest and most powerful institution that insists on calling itself that.
But, even setting all that aside, all you’ve proven is that finding common ground between two disagreeing viewpoints is insufficient. If you had to find a point of agreement between the US, USSR, and whatever disgruntled Trotskyites you could find, you’d address that point of disagreement as well.
> I know there are Marxists who claim that the USSR wasn’t even properly socialist,
You don't have to be a Marxist to claim that the USSR wasn't properly "socialist." You just have to read whoever you think lays out a clear definition of socialism, and compare it to the government of the USSR as observed.
When your analysis of the facts of the situation values the power dynamics of differing groups of adherents to fringe radical movements over simple observation and checking of requirements off of a list, you're caught up in political drama, not ideological drama.
It's a semantic argument and I'm not attached to any particular definition of socialism. Also, I find that most arguments that "the Soviet Union wasn't actually socialist" are disingenuous attempts by socialists to deflect from the fact that their ideas have never actually worked in practice, but that's beside the point somewhat.
Arguing about whether the Soviets were “true” Marxists is like arguing about whether the Roman Catholic Church is the “true” “catholic and apostolic church” of the Nicene Creed; at some point everyone who isn’t a theologian taking a break from the equally important “angels dancing on the head of a pin” problem just uses the word “Catholic” to refer to the biggest and most powerful institution that insists on calling itself that.
But, even setting all that aside, all you’ve proven is that finding common ground between two disagreeing viewpoints is insufficient. If you had to find a point of agreement between the US, USSR, and whatever disgruntled Trotskyites you could find, you’d address that point of disagreement as well.